Friction-release distal latch implant delivery system and components

This application claims the benefit of U.S. Provisional Application Ser. Nos. 61/039,863, filed Mar. 27, 2008, and 61/158,456, filed Mar. 9, 2009, each of which is hereby fully incorporated by reference.

The subject matter described herein relates generally to systems, devices and methods for the delivery of textured (e.g., braided or woven) medical implants.

US Patent Publications 2006/0271149 and 2006/0271153, assigned to CHESTNUT MEDICAL TECHNOLOGIES, INC., disclose delivery systems for braid-type stents. In one example system, a distal coil socket holds the distal end of the braid stent until the braid is retracted by grippers holding the proximal end. These grippers are able to maintain contact with the proximal end through compression by an external sleeve surrounding the grippers. Upon sleeve withdrawal, the grippers release the proximal end of the stent.

System miniaturization of the referenced system(s) is limited by the gripper configuration. Also, the lack of a release mechanism for detachment from the distal socket presents issues of inadvertent deployment and/or non-optimal control. Accordingly, there remains a need for both more robust/reliable and potentially further downsizable systems for advanced braid-type implant delivery. The present invention offers such systems with various advantages as presented herein and others as may be apparent to those with skill in the art.

The systems, methods and devices described in this section and elsewhere herein are done so by way of example embodiments. These example embodiments are provided to aid in the description of the inventive subject matter and are in no way intended to limit the inventive subject matter beyond the express language of the claims. For example, the inventive subject matter described herein is directed towards implant securement through releasable surface friction generated between a textured implant and a textured delivery device, example embodiments of which are braided implants and multi-filar or braided delivery devices. However, this inventive subject matter is not limited solely to the use of braided or multi-filar configurations as one of skill in the art will appreciate, based on this disclosure, that other textured configurations can likewise provide satisfactory surface friction. Thus, the embodiments provided herein for this and all other features are merely non-exhaustive examples.

Provided herein are systems, devices and methods for implant delivery with a device that holds the implant in a state of frictional lock. This application claims the benefit of U.S. Provisional Application Ser. Nos. 61/039,863, filed Mar. 27, 2008 and 61/158,456, filed Mar. 9, 2009, each of which is hereby fully incorporated by reference. The implant is preferably (i.e., has been selected as but is not necessarily) a stent and its distal end portion is held onto a core construct in a state of frictional lock by a distal housing (or latch). A proximal housing or other holding or grasping device can be used to retain the proximal end portion of the implant in a state of frictional lock or otherwise. The core construct can comprise an elongate tubular textured member, e.g., a braided or multi-filar sleeve, slidable over an elongate core member (or central wire). The sleeve preferably includes at least an accessible (or exposed) distal textured interface for contact with a corresponding textured surface on the implant. The sleeve can also include an optional proximal textured interface for contact with a corresponding textured surface on the implant. These interfaces are preferably present about the periphery of the sleeve, but can also be limited to smaller regions, with the distal implant interface being adjacent the distal end of the sleeve. In a preferred example embodiment, the sleeve is a braided tube that is covered (or jacketed) between the implant interface regions. The covering is preferably fixed to the braid and can be formed from a heat-shrinkable tube, extrusion, and the like.

Alternatively, or additionally, a proximal portion of the braid may comprise a secondary jacket to stiffen it relative to one or more distal and more flexible sections. Such a construction for the sleeve is highly pushable, torqueable and kink-resistant. Moreover, in a braided configuration, the sleeve can have its PIC (Per Inch Crosses) varied along its length to provide enhanced distal flexibility. In other words, the sleeve may be tuned/modified as a catheter-like subcomponent of the system. In an alternative embodiment, an elongate polymeric, metallic or metal alloy shaft can be used with sections of braid attached (e.g., clamped, glued, embedded or the like) to the shaft surface to form the interfaces with the implant.

Similarly, the core member can also be configured for enhanced flexibility. For example, the core member may have one or more successively tapered regions near or adjacent to its distal end, like a typical guidewire. The core member is preferably coupled with an atraumatic distal end (e.g., a floppy coil tip). Both the core member and the sleeve can comprise an elastic or superelastic materials such as stainless steel, NiTi, CoCr, other alloys, polymeric materials and the like.

The tubular implant preferably has textured distal and proximal surfaces (which may be continuous or disconnected). These surfaces are preferably present about the entire inner periphery of the implant, but can also be located in limited regions generally corresponding to the interface regions of the sleeve. In a preferred embodiment, the implant is a braided implant with a braided surface about its entire exterior. However, other configurations of implants having grafts, coatings (e.g., lubricious, drug-eluting, and the like) or other non-textured surfaces present on the exterior of the implant are possible. See, e.g., U.S. Pat. No. 4,416,028 to Eriksson, et al.

The tubular implant is expandable from a contracted state to an expanded state, and preferably self-biased towards the expanded state. Generally, expansion results in lengthwise shortening of the implant. Thus, holding the end portions of the implant stretched apart from each other (such as in the state of frictional lock described herein) can cause the implant to be maintained in a contracted state, without the need to radially restrain the entire implant (such as with a full body sheath). If the implant is self-biased to expand, release of the end portions allows the implant to expand into apposition with tissue at the implantation site. Else, a secondary expansion device can be used, such as an inflatable balloon or mechanical arms.

The frictional lock described herein relies on a high degree of surface friction between the implant and an underlying surface to resist longitudinal/axial motion of the implant (in its contracted state) along the longitudinal axis of the delivery device or sleeve. Substantial surface friction between implant and the underlying surface will prevent the implant from sliding relative to the underlying surface, preventing the implant from decreasing in length (i.e., for shortening) and radially expanding.

Although the term “lock” can be used, it should be understood that the implant is not locked from all movement in an absolute sense, as the implant can be forced from the lock should sufficient force be applied to overcome the surface friction. Rather, the implant is preferably locked in place sufficiently to resist the implant\'s own bias towards expansion (if any), to resist bias applied by a secondary expansion device (if any), to resist forces applied against the implant while maneuvering within the patient\'s vasculature (e.g., forces applied either by the delivery device or the patient\'s vasculature or blood flow), and/or to resist forces applied to the implant during any loading, unloading, or deployment procedures. Of course, one of skill in the art will appreciate that the degree of surface friction necessary to achieve the state of frictional lock will depend on the specific delivery device implementation and intended application(s).

It has been found that certain textured surfaces, when in opposition to each other, are capable of exhibiting sufficient surface friction to form a frictional lock for implant delivery. The term “textured” is not intended to imply the use of any particular material or manufacturing process (e.g., an applied finish or coating). Instead, the term “textured” is used in a basic sense only to refer to surface profile, namely, a non-level or high-friction surface profile, as opposed to a level, smooth or polished surface profile. Certain of these textured surfaces can be formed from many smaller, discrete constituents in close proximity with each other, such as with braids, meshes, matrices and fabrics, which are generally formed from one or more layers of woven or interleaved strands, threads or wires, and multi-filar materials, which are generally formed from windings or coils of strands, threads or wires. Examples of these used to create frictional lock (implant-to-sleeve or sleeve-to-implant) include braid-to-braid contact, multi-filar-to-multi-filar contact, and braid-to-multi-filar contact. The same or similar configurations of the textured material generally generate the greatest surface friction, i.e., two braids having the same number and size of constituents, identical PIC and pitch (the angle of the constituent with respect to an axis of the braid), since the opposing constituents are readily placed in interfering/interlacing contact with each other. These configurations also have the advantage that flexing, twisting or stretching can force the constituents into even greater contact or interference, further increasing the frictional lock. Other textured surfaces can be formed on a body by deforming this surface to create a textured pattern, e.g., by etching, grinding, sanding, and the like. Still other textured surfaces can be formed by applying a high-friction coating to a body. Of course, any combination of these can also be used (e.g., a braid implant on a patterned underlying surface, etc.).

The implant is preferably held engaged with the underlying interfaces by a distal and a proximal housing (or cover) that closely fits over at least the distal and proximal end portions of the implant, respectively, such that the implant is held (or constrained) in contact with or against the respective underlying interfaces of the sleeve. Should it be desired, the core member can abut the sleeve from the interior, to resist inward deformation by the sleeve when the implant is pressed against it by the housings. Here, the implant is frictionally locked when held against the sleeve by the distal and/or proximal housings. It should be noted that the entire end portion of the implant need not be housed by a continuous covering, only so much as to adequately hold the implant end portion in the contracted state and in frictional lock with the underlying surface.

In one example embodiment, at least one of the distal and proximal housings are moveable with respect to the other to release the implant from frictional lock. For example, the distal housing can be fixed to the core member and can slide relative to the sleeve or proximal housing by movement of the core member. Advancement of the distal housing off of the implant releases the distal lock. The proximal housing can be a retractable tubular member placed over the sleeve and can slide relative to the sleeve or distal housing. Retraction of the proximal housing releases the proximal lock.

In another example embodiment, the distal housing can be fixed to the sleeve, with the core member remaining slidable within. The core member preferably includes a distally-located wedge-like portion that holds the sleeve in an open state against the implant from the interior at the distal interface (and also, optionally, the proximal interface). The distal lock can be released by proximally retracting the core member within the sleeve, which allows the sleeve (advantageously heatset or otherwise set to a smaller diameter) to collapse/withdraw from the distal textured portion of the implant and reduce the degree of contact (partially or entirely) with the implant. The proximal lock can be similarly released (in which case it can be fixed to the sleeve) or the proximal housing can optionally be made retractable as described above.

In one example embodiment, the distal and proximal housings are configured as tubular sheaths. These tubular sheaths can, for example, be formed by heat-shrinkable tubing. The heatshrink for the housings, and the jacket described above, may be PE (polyethylene), PET (polyester), or the like. PI (polyamide), FEP, PEEK and other materials may also be advantageously employed. The housings can be formed in sections of the tubular sheaths that have a relatively larger diameter than adjacent sections, e.g., the housing can be a section of the sheath that shoulders outward.